In the field of industrial chemical synthesis, the improvement of the yield and selectivity of chemical processes bears considerable impact on the industry. Particularly, the focus in said improvements is on lowering costs, simplifying unit operations and environmental considerations. These three factors are particularly important in the field of agrochemicals where the volume of chemicals is large and the marginal profit is relatively small.
Of the many agrochemical compounds which are synthesized by multi-stage synthesis, methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate (chemical common name: azoxystrobin), particularly drew the attention of the present inventors. Azoxystrobin, disclosed in U.S. Pat. No. 5,395,837, is a plant protection fungicide with protectant, curative, eradicant, translaminar and systemic properties. The preparation of azoxystrobin as described in Example 3 of U.S. Pat. No. 5,395,837 involves an aromatic substitution reaction between 2-cyanophenol and (E)-Methyl 2-[2-(6-chlorpyridimin-4-yloxy)phenyl]-3-methoxypropenoate also known as (E)-Methyl-2-[2-(6-chloropyrimidin-4-yloxy)-phenyl]-3-methoxyacrylate, at temperatures at 95° to 100° C. in DMF in the presence of stoichiometric amounts of potassium carbonate and a catalytic amount of copper(I) chloride. The reported yield of azoxystrobin is 65% wherein the product was found to have a melting point of 110° C.-111° C., indicating a final product of relatively low purity, which subsequently required further purification. It has been suggested that reactions of 2-cyanophenol or other isomers of cyanophenol or phenols in general under conditions of temperatures of about 90° C. and above, in the presence of basic reagents which can promote the formation of phenolate salts, may cause polymerization and the formation of tars. This clearly is a highly undesirable side effect.
Accordingly there is an ongoing and long felt need for a process for aromatic substitution reactions in the presence phenols with improved yield and selectivity.
Thus, it is the objective of the present invention to provide a process for reacting phenols under basic conditions in which the yield and selectivity is improved.
Other objectives of the invention shall become apparent as the description proceeds.